Numerous studies have attempted to measure the automobile's ecological footprint, a process fraught with assumptions and sketchy data. Still, the eco evidence is overwhelmingly against the car and the vast systems that manufacture and support it. Estimates size the ecological footprint of the 134 million passenger cars in the United States as slightly larger than the state of Texas. That's leaving out the legions of SUV's and other light trucks, not to mention heavy-duty trucks.
Put another way, if the 6 billion people on this planet can each lay an even claim to 3.95 acres of land as their fair ecological footprint, then the 1.48 acre per car eco-footprint of the average U.S. sedan means 41 percent of your ecological capacity is sitting in your driveway. Even if the numbers are well off reality, your car represents a major ecological burden.
Where does that burden come from and what can you do about it? A fair assessment includes all activity, from digging the iron out of the ground to recycling the remains, but in this short article, we'll concentrate on the more direct consequences associated with owning and fueling a modern sedan and leave the infrastructure questions to the policy makers.
Gasoline and CO2
Such an approach addresses the major concern, as it turns out. Estimates attribute 77 percent of a car's footprint to the CO2 released from burning gasoline. If three quarters of your car's eco-footprint is attributed to its ability to release CO2, then you can have a real impact simply by limiting the amount of gasoline you burn.
Gasoline consumption is important because CO2 production is directly related to gasoline combustion. The chemical result of burning gasoline is water and CO2, so ignite gasoline and you get CO2. Lots of CO2.
In fact, this relationship between gasoline and CO2 is so strong that any time you read of a "carbon limit" or "CO2 tax" or "CO2 limit" you can read that as a "gasoline tax" or "gasoline consumption limit." It's that simple.
It also means that if you want to reduce your car's eco footprint, riding a bicycle, walking or simply staying at home is likely the greatest influence you can have.
Maximizing Your MPG
The next best thing to not driving is maximizing your car's miles per gallon. There are many tricks for increasing fuel mileage, but the best one is inflating your tires to the recommended level (it's amazing how often this is 32 psi), then checking and adjusting the pressure religiously, at least once a month. Tires naturally lose approximately 2 percent of their air pressure per month, and low tire pressure takes more power—and thus more fuel—to rotate. And do we really need to point out that if you're buying a new car, higher EPA fuel mileage estimates help?
Another major benefit comes from limiting speed to 65 mph or less. By then you are paying a logarithmically increasing price in fuel consumption due to wind resistance. And as if you could avoid it, idling in traffic is an obvious waste of time and fuel, so you also have a green reason to skipping rush hour.
Emission Controls
Then there are toxic emissions including hydrocarbons, carbon monoxide, oxides of nitrogen—the gasses measured during an emissions test. Current emission controls have largely corralled these bad actors, and the newer the car, the more emissions are reduced.
Thanks to advanced emission controls a few conventional gasoline-powered cars, Ford's Focus PZEV (Partial Zero Emission Vehicle) for example, produce minute fractions of the pollutants from an unregulated engine. Indeed, on the smoggiest days in places such as Los Angeles, a PZEV actually exhausts cleaner air than it ingests. That's a rare case, but it illustrates just how far we've come in cleaning up our automotive act.
For efficient pollution control it is necessary to have up-to-date emission control devices and to keep them in working order. In practical terms that means driving a newer car and adhering to its maintenance schedule. Here we must find a balance between replacing a vehicle that we've already paid a high ecological price to build and one that works better from an emissions standpoint. Currently emission controls are mandated to work for 150,000 miles, which gives a reasonable guide to replacing a car.
Then there is the argument about driving an older vehicle, but fewer miles. To a point this is sound, but the decrease in pollutants from newer cars is so great that once a car is much older than five years it doesn't take much driving for it to equal or notably exceed the emissions of a new daily driver. Still, for truly occasional-use vehicles it probably makes sense to keep an older one handy.
This is especially true if the older vehicle is kept in good repair, and is not a gross polluter. A gross polluter can be an old or new vehicle, and is one that egregiously spews harmful emissions due to a poor tune, worn out or missing emission equipment or a worn out engine.
Even a new car with a minor, barely detectable mechanical problem can equal the smog output of hundreds of correct-running newer vehicles, and a slightly older car with a tight engine, a good tune and operating emission equipment is much cleaner than a problematic new car. So if you keep an older pickup truck just for hauling the boat to the lake or scraping snow off the driveway, keep it in good shape and don't feel so bad about it.
Recyclables
Let's not forget the consumables, notably oil, tires and batteries. All can be recycled, and with used motor oil that's a very good thing as a quart of oil swept down a storm drain will ruin 250,000 gallons of drinking water. Tires are a special problem; their steel belts make them tough to cut or grind, but their approximately 13 percent oil content often makes them worth the trouble.
Of the 99 million automotive batteries manufactured each year the EPA says nearly 90 percent are recycled. But their main ingredient, lead, is nasty stuff. This has made it economical to export battery recycling to places where pollution controls are lax, which also tends to concentrate the problem. Still, of the lead and plastic materials in new batteries, it's thought 60 to 80 percent of it is recycled.
The figures are similar for the car itself when it finally hits the wrecking yard. One of the most highly recycled items in the U.S., the percentage of a car that is eventually recycled is typically quoted between 75 and 80 percent. And the steel content is an especially happy story, as 98 percent of it makes it to a smelter for reuse.
Future-tech holds some promise, but nothing revolutionary in the near term. Hybrids and electric cars would seem to help, but it depends. A hybrid driven on the freeway holds little emission or consumption benefit, but it does in stop-and-go driving. It also shares an issue with the pure electrics, which is handling all those batteries and avoiding complications when they inevitably collide in accidents. Besides, a pure electric often just moves the pollution and CO2 release from the car to a distant power plant.
If that's a coal-fired plant you haven't done any good, a nuclear station would be leagues better. Clean diesels are coming, and they do offer a significant 30 percent reduction in fuel consumption—read that as CO2 production—compared to current gasoline engines. They likely offer the best short-term improvement.
For now, pump up your tires, keep up on maintenance and consolidate trips. The car, so flexible, powerful and private, is the proven winner in personal transportation. Incremental improvements along each step of its lifecycle will make it easier to live with.
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